An object of the present invention is to impose a penalty on a player, without causing a sudden deceleration, when a moving body moving on a course formed in a virtual space contacts a sidewall at the edge of the course. To achieve this object, assume that a vehicle running on a course formed in a virtual space has contacted a sidewall at point A which corresponds to the 0.sup.th frame. Whereupon, at point B which corresponds to the 1.sup.st frame, an amount, Rf, is subtracted from vehicle speed V, and from the 2.sup.nd frame until point C which corresponds to the 60t.sup.th frame, processing to subtract RSd from vehicle speed V is successively performed.